Fast Simplex Link is a 32-bits wide interface on MicroBlaze. The FSL channels are uni-directional, point-to-point data streaming interfaces. The FSL can be used for extending the processor execution unit with custom hardware accelerators thanks to a low latency dedicated interface to the processor pipeline. In addition, the same fsl channel can be used for the transmit or receive either control or data words. A separate bit indicates whether the transmitted (receive) word is control or data information.
References
Fast Simplex Link Wikipedia(Text) CC BY-SA